Control of fluidic devices

ABSTRACT

A pressure change suitable for the control of a fluidic switch can be achieved without the use of movable valves by the application of ultrasonic vibrations to a nozzle producing a jet of fluid directed at a coaxial collector orifice. Either collector orifice may be the inlet end of a preferably sharpedged dynamic-pressure tube, and the pressure in this tube utilized, or the collector tube may be used as a vent of a vessel in which the jet is formed, the change in the pressure in this vessel due to the application of the oscillations, which may be a change from negative to positive relative pressure, being then utilized as a control pressure.

lllnited States Patent Moss et a1,

[4 1 Jan, 25, 1972 154] CONTRUIL 0F FLUIDIC DEVICES Norman Moss, llford;Michael John Broad,

[72] Inventors: Enfield, both of England [73] Assignee: The PlesseyCompany Limited, llford, En-

gland [22] Filed: June 2, 1970 [21 1 Appl. No.: 42,634

[30] Foreign Application Priority Data June 24. 1969 Great Britain..31,730/69 [52] .....137/81.5 [51] ..Fl5c 3/12 [58] ..137/81.5, 83;346/75 [56] References Cited UNITED STATES PATENTS 3,386.343 6/1968 Gray....137/83 X 3.500.850 3/1970 Kelley ..137/8l.5 3.334.641 8/1967Bjornsen ..137/83 X 2,128,682 8/1938 Von Manteuffel 1 37/83 3.144.0378/1964 Cargill et a1. 137/81 5 3.266.513 8/1966 Voit, Jr 137/8153,281,860 10/1966 Adams et al. .....346/75 3,298,030 1/1967 Lewis et a1.346/75 3,3 79,204 4/1968 Kelley et a1. ..137/81.S 3,406,701 10/1968Meulendyk 1 137/83 3,454,025 7/1969 Egli 1 37/815 PrimaryExaminer-Samuel Scott Attorney-Blum. Moscovitz, Friedman & Kaplan 57ABSTRACT A pressure change suitable for the control of a fluidic switchcan be achieved without the use of movable valves by the application ofultrasonic vibrations to a nozzle producing a jet of fluid directed at acoaxial collector orifice. Either collector orifice may be the inlet endof a preferably sharp-edged dynamic-pressure tube, and the pressure inthis tube utilized, or the collector tube may be used as a vent ofavessel in which the jet is formed, the change in the pressure in thisvessel due to the application of the oscillations, which may be a changefrom negative to positive relative pressure, being then utilized as acontrol pressure.

7 Claims, 2 Drawing Figures INPUT ELECTRIC OUTPUT 'A' PATTENIED M25 I972INPUT ELECTRIC I2 (FLUID/C ou TPUTB' FLU/DIG SWITCH FLUID/C OUTPUT ACONTROL ()ll FLUiDlC DEVKCIES This invention relates to fluidic devicessuch as fluidic monostable or bistable switches and fluidic amplifiers.Such fluidic devices are generally operated by gaseous fluids, and theinvention has for an object to provide electrically operable controlmeans for such devices whichdo not involve the use of mechanical valvesor other devices subject to wear. According to the present inventioncontrol is effected by applying to a nozzle by which a jet of operatingfluid is produced and directed at an aperture aligned with the jetnozzle, ultrasonic vibrations in the longitudinal direction of the jet"When the jet nozzle is subjected to such ultrasonic vibrations, thedynamic pressure near the axis of the jet, and therefore pressurebuildup in the aligned orifice, is substantially decreased, and thisdecrease in dynamic pressure may be utilized as a pressure signalresponsive to the application of the ultrasonic vibrations. Thephenomenon may be explained by assuming that the application ofultrasonic vibrations tends to transform a solid, compact jet into anexpanding cone-type spray. This is known to occur when ultrasonicvibrations are applied to a nozzle by which a jet of liquid fuel isinjected into a gaseous atmosphere, and the occurrence of a similartransformation in the case of a gaseous jet is suggested by the factthat we have also found that when a baffle having a through orifice isplaced between a jet nozzle fed with air and an aligned collector nozzlewith the baffle orifice in axial alignment with both nozzles, theapplication of ultrasonic longitudinal vibrations to the jet nozzleincreases the force exerted upon the baffle in the direction of the jetwhile at the same time reducing the pres sure measured at the collectornozzle.

According to a modification of the invention, the aligned orifice orcollector nozzle may be used as a vent and the variation of the pressurein a chamber enclosing the jet from the jet-producing nozzle to theoutlet orifice may be used as a control pressure for fluidic apparatus.In this case the application of the ultrasonic vibrations to the jetnozzle will result in a considerable increase in the control pressuregenerated. If the chamber is so constructed that in the absence ofultrasonic vibrations a suction effect is produced in the chamber, theapplication of ultrasonic vibrations can be arranged to cause thesuction to be changed to an excess pressure, thus utilizing theultrasonic vibrations to reverse the sign of a control pressure with aview, for example, to causing a piston to move towards one end of itsstroke in the absence, and towards the other end of its stroke in thepresence, of ultrasonic vibrations.

The term ultrasonic vibrations is utilized in this specification toindicate vibrations of a frequency high enough to result in considerablevariations of the type of jet issuing from the jet nozzle. The lowerlimit of this range has been found in many cases to substantiallycoincide with the audibility limit for an average human ear, being forexample between and [5 kHz.

Two alternative embodiments of a control-pressure generating deviceaccording to the present invention as applied to a fluidic element willnow be described in more detail by way of example with reference to theaccompanying drawing, in which FIG. 11 is a diagram of part of a fluidicsystem including an axial section of the device, while FIG. 2 is afragmentary axial section illustrating a modified form of collectornozzle.

Referring now first to FIG. l, a gaseous fluid, for example air underpressure, is fed by a flexible pipe l to a nozzle chamber 2 which isformed in a metal body 3 to constitute a noule passage, and which has asharp-edged outlet nozzle d hereinafter called jet nozzle. This jetnozzle opens into a vessel 8 which, like the body 3, forms part of abody structure and will, when fed with fluid from the pipe ll, produce areasonably compactjet 5 of the fluid. Aligned coaxially with thejetnozzle 4 and the jet 5 is a collector nozzle consisting of a tube 6,which is connected to a flexible conduit 7 so that, so long as the flowpermitted through the tube 6 is kept small in comparison to the massflow through the jet nozzle 4, the tube 6 may be considered toconstitute a dynamic-pressure nozzle, so that a pressure will be builtup in the tube 6 which exceeds the static pressure in the vessel 8 inwhich the jet-forming nozzle 4, the jet 5, and the orifice of thecollector nozzle 6 are confined, by the dynamic pressure of the jet 6 atthe entrance to the tube 6. The metal body 3 containing the chamber 2,and a generally similar balance body 9, are arranged at opposite sidesof a piezoelectric element llt) to form an electromechanical transducerwhich, when electrical energy of ultrasonic frequency is applied to thepiezoelectric element 10 by terminal wires ill, will produce ultrasoniclongitudinal oscillations of the jet nozzle 4. We have found that, whenultrasonic vibrations are thus applied to the nozzle 4, the pressurebuilt up in tube 6 and conduit 7 will fall considerably as compared tothe pressure produced by the jet in the absence of such ultrasonicvibrations, and accordingly the conduit 7 may be connected to, forexample, the control-jet inlet of a fluidic switch 16a in order toperform a fluidic switching operation. The vessel 8 is formed with alateral aperture 12 which, for this use of the apparatus, will be leftopen to the atmosphere.

In an alternative mode of use a conduit 13 is connected to the lateralaperture 112 of the vessel 8, and the outlet of the tube 6 is exposed tothe atmosphere. In this case, provided the tube 6 and the nozzle 4 aresuitably arranged and dimensioned, the supply of air through the tube llmay be arranged to normally produce suction inside the vessel 8, whichcan be transmitted by the conduit 13 to a fluidic device to becontrolled and shown in the drawing as a fluidic switch 11612; theapplication of suitable electric power to the terminals 11 and thus ofultrasonic vibrations to the nozzle 4 will then cause the pressure inthe vessel 8 to rise, preferably above atmospheric pressure, thusproviding a means for applying to the fluidic device 16b, through theconduit 13, a pressure which, compared with atmospheric pressure,changes from negative to positive when electric power is applied to thepiezoelectric element 10 by the wires ll.

FIG. 2 illustrates a modified collector tube 6a which may be substitutedfor the collector tube 6 of FIG. 1, more particularly when the pressuredeveloped in the collector tube is to be utilized for controlling afluidic device. This tube 6a is tapered at its inlet end by conicalformation of its outside surface so as to present to the flow a knifeedge. This feature has been found to emphasize the change of pressure inthe collector tube achievable by the application of ultrasonicvibrations to the nozzle 4.

Referring now once more to FIG. 1, an optional feature of theillustrated apparatus consists in the provision of a baffle plate 14which has an aperture 115 aligned with the jet 5. This arrangement hasbeen found to be capable, if the baffle plate is suitably placed andshaped, of increasing the available percentage change of dynamicpressure as measured by the tube, although this percentage increase maybe accompanied by a reduction in the total dynamic pressure observed inthe tube.

It may be added that in preliminary experiments employing a jet nozzleand a collector tube of about 0.5 mm. inside diameter each, theapplication of a 20 w. electrical input at 50 kHz. to a piezoelectricoscillator for the jet nozzle could be made to result in a substantiallyproportional 45 percent reduction in the recoverable pressure head overan air speed range of between 0 and 20 cm. H O in the collector tube 6,while the replacement of the tube 6 by a sharp-edged tube 6a resulted ina reduction in the recoverable pressure head during the application ofthe oscillations which in some cases was as high as 50 to 55 percent.

We claim:

1. An electric control device for a fluidic-pressure output, whichcomprises a body structure, a jet-forming nozzle in said body structure,said nozzle being adapted for connection to a fluid-pressure supply andhaving an outlet for producing a jet of such fluid, said body structurehaving a collector aperture aligned with such jet in spaced relationfrom the nozzle outlet and a further aperture communicating with boththe nozzle outlet and the collector aperture but clear of the path ofsuch jet, one of said apertures being adapted for connection to acontrol inlet of a fluidics device and the other aperture being open tothe ambient atmosphere, and electromechanical transducer means adaptedfor connection to an electric control input and associated with thenozzle for, when energized, applying to the nozzle and the fluid passingthrough it ultrasonic oscillations in the longitudinal direction of thejet produced by the nozzle.

2. A control deviceas claimed in claim I, in combination with a fluidicdevice having a control-pressure inlet connected to said one aperture.

3. A control device as claimed in claim 1, wherein the collectoraperture is adapted for connection to such control inlet.

4. A control device as claimed in claim 3, which includes a collectortube aligned with the jet nozzle and having its end facing the latterformed as a knife edge.

5. A control device as claimed in claim 1, wherein the further apertureis adapted for connection to such control inlet.

6. A control device as claimed in claim 5, which includes a baffle platefixedly connected to the body structure, said plate extending across thejet and having an aperture aligned with the jet.

7. A control device as claimed in claim 6, in combination with a fluidicdevice having a control-pressure inlet connected to said one aperture.

1. An electric control device for a fluidic-pressure output, whichcomprises a body structure, a jet-forming nozzle in said body structure,said nozzle being adapted for connection to a fluid-pressure supply andhaving an outlet for producing a jet of such fluid, said body structurehaving a collector aperture aligned with such jet in spaced relationfrom the nozzle outlet and a further aperture communicating with boththe nozzle outlet and the collector aperture but clear of the path ofsuch jet, one of said apertures being adapted for connection to acontrol inlet of a fluidics device and the other aperture being open tothe ambient atmosphere, and electromechanical transducer means adaptedfor connection to an electric control input and associated with thenozzle for, when energized, applying to the nozzle and the fluid passingthrough it ultrasonic oscillations in the longitudinal direction of thejet produced by the nozzle.
 2. A control device as claimed in claim 1,in combination with a fluidic device having a control-pressure inletconnected to said one aperture.
 3. A control device as claimed in claim1, wherein the collector aperture is adapted for connection to suchcontrol inlet.
 4. A control device as claimed in claim 3, which includesa collector tube aligned with the jet nozzle and having its end facingthe latter formed as a knife edge.
 5. A control device as claimed inclaim 1, wherein the further aperture is adapted for connection to suchcontrol inlet.
 6. A control device as claimed in claim 5, which includesa baffle plate fixedly connected to the body structure, said plateextending across the jet and having an aperture aligned with the jet. 7.A control device as claimed in claim 6, in combination with a fluidicdevice having a control-pressure inlet connected to said one aperture.